In the formation of integrated circuits on the surface of a semiconductor substrate, oxide or oxynitride films are frequently grown or deposited over the surface of a crystalline substrate such as silicon. Industry standard processes for chemical vapor deposition (CVD) of high quality silicon oxide (SiOx, x≦2) films for semiconductor Flash memory and micro-feature sidewall applications are based on high-temperature reactions of dichlorosilane (DCS) and nitrous oxide (N2O), for example. The main benefits of this process include the ability to process multiple substrates simultaneously in a batch process, excellent electrical performance of the silicon oxide films, and relatively low wet etch rates of the films compared to other CVD films, e.g., films deposited using tetraethyl orthosilicate (TEOS), bis(tertiary-butylamino)silane (BTBAS), and other precursors.
However, there are several shortcomings associated with performing CVD of silicon oxide films using DCS and N2O. This CVD process requires relatively high substrate temperature (e.g., around 800° C.) which can limit its use when integrating silicon oxide films with advanced materials that require a low thermal budget. Further, the use N2O gas as the oxidizing gas has been found to result in poor and generally uncontrollable nitrogen (N) incorporation into the silicon oxide films. Low film deposition rates are thought to be due to a rate limiting DCS nucleation step on the oxide film that is due to absence of gas phase reactions between DCS and N2O.
The demand for high-k dielectrics has required manufacturers to augment existing oxide films (e.g., oxide films on silicon and germanium) by incorporating nitrogen into the oxide films. It is known in the art that nitrogen incorporation into the oxide films increases the dielectric constant of the resulting oxynitride film, and allows thinner gate dielectrics to be grown on these semiconductor substrate materials. Silicon oxynitride (SiOxNy) films can have good electrical properties, including high electron mobility and low electron trap density that are desirable for device operation in semiconductor applications. Further advantages of nitrogen incorporation in a thin silicon oxide film include: reduced boron penetration through a p-doped polysilicon gate, improved interfacial smoothness, increase in the dielectric constant of the silicon oxynitride film, and improved barrier properties to prevent diffusion of metal oxides or metal gate materials into the underlying substrate.
Due to the miniaturization of semiconductor devices and use of advanced materials that require reduced thermal budgets of semiconductor processing methods, there is a need for new processing methods that provide low temperature silicon oxide and silicon oxynitride films deposition with high nitrogen incorporation at controlled depths while providing a controlled rate of oxide growth.